The full scale of the gas flaring undertaken by the North Dakota fracking industry has been laid bare, after a new report suggested the practice resulted in approximately $1bn of gas being wasted last year.

The new study from the Ceres group of sustainable investors draws on official figures from the North Dakota Industrial Commission and reveals that the state's oil and gas developers flared 29 per cent of the natural gas they produced during May 2013. The proportion of gas being flared has actually fallen from a peak of 36 per cent in September 2011, but the rapid expansion of the sector means that the total volume being flared is continuing to rise.

The analysis calculates that flaring throughout 2012 saw $1bn of gas burnt, resulting in greenhouse gas emissions equivalent to putting an additional one million cars on the road.

"The US is now one of the top 10 flaring countries in the world, primarily due to the rapid growth of flaring in North Dakota," said Ryan Salmon, the report's lead author and manager of Ceres' oil and gas program, in a statement. "Although the state's oil and gas industry is stepping up its efforts to curb flaring, the total volume of flared natural gas continues to grow. Investors are looking for producers and regulators to take more aggressive action to prevent the loss of this valuable fuel."

The high cost of oil relative to gas means many developers who are drilling for oil are failing to invest in the infrastructure needed to capture the gas and natural gas liquids that are released alongside the oil.

Investors and officials in North Dakota are now expected to step up pressure on developers to limit levels of flaring and ensure that gas is captured and sold.

For example, the state has set a target of limiting flaring to 10 per cent of production, although it is yet to set a date for when the target should be met.

Investors are similarly calling on developers to bring an end to the wasting of a valuable resource. "The flaring of natural gas is a tremendous economic waste, and it threatens the oil and gas industry's license to operate, as well as the environment," said Pat Zerega, senior director at Mercy Investment Services, which successfully urged leading North Dakota oil producer Continental Resources to set a flaring reduction goal earlier this year. "As oil and gas developments expand into more remote regions like North Dakota, the issue of flaring will continue to be a concern for investors, the environment and the industry.

However, the report, entitled Flaring Up, warns that the continued expansion of the industry means that unless the percentage of flared gas falls below 21 per cent volumes of flared gas will continue to rise through to 2020.